Embryonic pancreas: The pancreas will be placed in organ culture and grown under conditions similar to those previously used on rat embryonic pancreas. With the medium used we have found that the islets undergo selective growth and development whereas the acinar cells completely disappear. Using human embryonic pancreas we plan to evaluate the various factors influencing the rate of cell division, the selective differentiation of the various types of islet cells, the biosynthesis of insulin, glucagon, and other islet hormones, and their release into the culture medium. At a future date these studies might provide suitable donor material for beta cell transplantation to human diabetic subjects. They may ultimately make it possible to correct the metabolic abnormalities characteristic of diabetes and to possibly prevent or delay the development of the serious complications of diabetes, i.e. blindness and fatal kidney disease.